RU2460106C2 - Liquid crystal display device - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: backlight module (60) is provided such that light (L3) incident from the backlight module (60) onto the liquid crystal display element (20) in the diagonal direction, which, with high probability, causes emission of light from the liquid crystal display element (20) in the normal direction, has a lower intensity than light (L2) incident from the backlight module (60) onto the liquid crystal display element (20) in another diagonal direction.

EFFECT: improved device.

18 cl, 26 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a liquid crystal display device, in particular to a liquid crystal display device capable of realizing high contrast display.

State of the art

Liquid crystal display devices are widely used as display devices. These liquid crystal display devices generally include, typically, a liquid crystal display element and a backlight unit. The liquid crystal display element has a structure in which a liquid crystal layer is placed between transparent substrates, each of which contains a polarizer. Additionally, the backlight unit is configured to backlight the liquid crystal display panel included in the liquid crystal display element, and includes a light source, a light guide, a diffuser, and the like.

Recently, it is required that liquid crystal display devices have higher brightness and higher contrast, etc. In response to these requirements, various technologies have been proposed.

Patent Document 1

The liquid crystal display element (liquid crystal display device) described in Patent Document 1 includes BEF (product name: short for “brightness enhancement film”), which is a reflective polarization brightness enhancement film made by Sumitomo 3M Limited. BEF boosts brightness, etc. liquid crystal display element. Additionally, a polarizing film (polarizer) on the side of the backlight module is provided with light scattering means.

Hereinafter, the liquid crystal display device of Patent Document 1 is described with respect to its specific configuration with reference to a cross-sectional view in FIG. 24, illustrating the configuration of a conventional liquid crystal display device. The liquid crystal display device 130 described in Patent Document 1 is configured such that a TN (twist-nematic) liquid crystal layer 106 is interposed between the substrates (transparent substrates) 102a and 102b, and polarizing films 101a and 101b are provided. In addition, a backlight unit 108 is provided on the rear side of the liquid crystal display device 130. The backlight module 108 mainly consists of a reflection plate 113, a lower diffuser plate 112, a light guide plate 111, and a BEF 110.

In addition, a film 109 containing scattering material is provided between the substrate 102b on the side of the backlight unit 108 and the polarizing film 101b.

Patent Document 2

The liquid crystal display device described in Patent Document 2 is configured such that the liquid crystal display element (liquid crystal display element) in which the twist-nematic liquid crystal (liquid crystal layer) is placed has a diffusion layer between the polarizing plate and the light guide plate, so that the scattering layer keeps the polarization state almost constant.

With this configuration, the liquid crystal display device described in Patent Document 2 allows for bright display.

Patent Document 3

The apparatus described in Patent Document 3 will now be explained with reference to FIG. 25, which is a cross-sectional view illustrating a configuration of a liquid crystal display device described in Patent Document 3.

As illustrated in FIG. 25, the liquid crystal display device 230 described in Patent Document 3 includes a liquid crystal display element 201 and a backlight (backlight module) 204. Two films 202 and 203 are provided between the liquid crystal display element 201 and the backlight 204. lenses. The lens films 202 and 203 are arranged such that the prism orientation directions 206 and 207 intersect at right angles, and the prism orientation direction 206 of the lens film 202, which is a lens film located closer to the liquid crystal display element 201, parallel to the transmission axis 205 of the polarizing plate which is on the incident light side of the liquid crystal display element 201.

With this configuration, the liquid crystal display device described in Patent Document 3 allows for display with high brightness.

Patent Document 4

The apparatus described in Patent Document 4 is explained below with reference to FIG. 26, which is a cross-sectional view illustrating a configuration of a liquid crystal display device described in Patent Document 4.

As illustrated in FIG. 26, the liquid crystal display device 330 described in Patent Document 4 includes a polarizing plate 305 on the light side (polarizer), a polarizing plate 306 on the light exit side (polarizer), a liquid crystal panel 304 between the polarizing plate 305 on the light incident side and a polarizing plate 306 on the light exit side and a backlight source 301 (light source) provided at the rear of the liquid crystal panel 304. The liquid crystal display device 330 The vision further includes a prism plate 308 between the polarizing plate 305 on the incident side of the light and the backlight source 301.

The direction A0 of the crest line of the prism plate 308 and the direction B0 of the transmission axis of the polarizing plate 305 on the incident side of the light intersect each other at right angles. With this configuration, the liquid crystal display device described in Patent Document 4 allows for display with a higher brightness.

Patent Document 5

The liquid crystal display device described in Patent Document 5 is configured such that a polarized light separating surface or the like. it is provided so as to be located toward the light exit plane of the flat optical fiber (light guide plate) of the backlight module, and a polarized light separating surface, and the like. can selectively reflect or pass the polarization component.

In this configuration, in particular, the brightness of the liquid crystal display device described in Patent Document 5 is increased in the normal direction of the display surface.

Patent document 1. Layout of patent application (Japan), Tokukai, number 2003-121847A (publication date: April 23, 2003)

Patent document 2. Layout of patent application (Japan), Tokukai, number 2003-15133A (publication date: January 15, 2003)

Patent document 3. Layout of patent application (Japan), Tokukaihei, number 8-22000A (publication date: January 23, 1996)

Patent document 4. Layout of patent application (Japan), Tokukai, number 2000-122046A (publication date: April 28, 2000)

Patent Document 5. Patent Application Layout (Japan), Tokukai, No. 2003-84283A (Publication Date: March 19, 2003)

Conventional liquid crystal display devices have the problem of having insufficient contrast.

In particular, the problem is that in a liquid crystal display device that uses a liquid crystal display element capable of realizing high contrast display (for example, a liquid crystal element with MVA mode), it is difficult to make the liquid crystal display element fully exhibit a high contrast characteristic that the liquid crystal display element is expected to have. The following description clarifies this aspect.

LCD display device configuration

FIG. 23 is a cross-sectional view of an example configuration of a liquid crystal display device 10.

As illustrated in FIG. 23, the liquid crystal display device 10 includes a liquid crystal display element 20 and a backlight unit 60 provided at the rear of the liquid crystal display element 20.

The liquid crystal display element 20 is configured such that the liquid crystal layer 22 is interposed between the first substrate 24 and the second substrate 26. On the first substrate 24, the first phase plate 30 and the first polarizing plate 34 are provided in this order. Similarly, on the second substrate 26, a second phase plate 32 and a second polarizing plate 36 are provided in this order.

Further, a polarizer reflection film with a brightness enhancement effect 40 is provided between the first polarizing plate 34 and the backlight unit 60.

The backlight unit 60 includes a light source (not shown), a light guide plate (not shown), two prism plates (a first prism plate 66 and a second prism plate 68), and an upper diffuser plate 70.

Light transmission process

Next, a process is explained in which light passes through the liquid crystal display device 10.

Whether or not light is emitted vertically from the backlight unit 60 in the direction of the liquid crystal display element 20 (L1 illustrated in FIG. 23), outward from the liquid crystal display device 10, depends on whether the liquid crystal layer 22 is in the ON or OFF state . Namely, while the liquid crystal layer 22 is in the ON state, light L1 is emitted outward from the liquid crystal display device 10 without blocking by the liquid crystal display element 20.

In contrast, while the liquid crystal layer 22 is in the OFF state, since the light L1 is blocked by the liquid crystal display element 20, the light L1 is not emitted from the liquid crystal display device 10.

It should be noted that the ratio (i) of the light intensity emitted while the liquid crystal layer 22 is in the ON state (light intensity when the state is ON) to (ii) the light intensity emitted while the liquid crystal layer 22 is in the OFF state (light intensity in the off state OFF), referred to as contrast (light intensity in the ON state / light intensity in the OFF state).

Typically, the light L1 that enters the liquid crystal display element 20 from the normal direction can realize high light intensity in the ON state and low light intensity in the OFF state according to whether the liquid crystal layer 22 is in the ON or OFF state.

In particular, for example, in the case where the liquid crystal display element 20 is a liquid crystal display element with an MVA mode capable of realizing high contrast display, light L1 incident from a vertical direction can realize contrast, for example, several thousand times.

Vertical light

It should be noted that in order to realize high contrast, in particular, it is important to reduce the light intensity in the OFF state while the liquid crystal layer 22 is in the OFF state.

In this regard, the light L1 that enters the liquid crystal display element 20 from the vertical direction of the liquid crystal display element 20 is likely to realize low light intensity in the OFF state.

This is because the light L1 that enters the liquid crystal display element 20 from the vertical direction of the liquid crystal display element 20 changes and passes as originally designed since the light L1 falls vertically on the polarizing plates (first polarizing plate 34 and second polarizing plate 36 ), phase plates (first phase plate 30 and second phase plate 32), a liquid crystal layer 22, and the like.

Oblique light

In contrast, the light (oblique light) L2 that exits diagonally from the backlight unit 60 and then diagonally enters the liquid crystal display element 20 differs from the light L1 in that the light L2 can reduce the contrast. The following description clarifies this aspect.

While the liquid crystal layer 22 is in the OFF state, the oblique light L2 is usually invisible to the viewer V, who is viewing the liquid crystal display device 10 from the front direction (hereinafter, the normal direction) of the liquid crystal display device 10.

Therefore, it is contemplated that the oblique light L2 does not cause a decrease in contrast when viewed from the normal direction.

Light deviation

However, the direction in which the oblique light L2 passes may vary. In particular, the light path may deviate toward viewer V in the liquid crystal display element 20 (see arrow L3 illustrated in FIG. 23).

Examples of various reasons for such a deviation of light occurring in the liquid crystal display element 20 include scattering in the liquid crystal layer 22, a color filter (not shown), and a TFT substrate (not shown).

Therefore, the oblique light L2, which is tilted with respect to the liquid crystal display element 20, is emitted from the liquid crystal display element 20 in the normal direction (the direction indicated by arrow L3 in FIG. 23) with a certain brightness level.

It is contemplated that the oblique light L2 does not affect the contrast when viewing from the normal direction. However, in fact, the light L2 is deflected in the direction of travel (sets the scattering) in the liquid crystal display element 20, and therefore, a part of the oblique light L2 is emitted in the normal direction, causing a decrease in contrast when viewing from the normal direction.

In particular, the light L1 that enters the liquid crystal display element 20 from the normal direction and the oblique light L2 have different light paths and different optical changes when the light L1 and L2 passes through the optical plates (e.g., phase plates and polarizing plates) the liquid crystal layer 22 and the like. Therefore, the light L1 and L2 has a different contrast. In general, a liquid crystal display device is configured to have better contrast when viewing from a normal direction. Accordingly, the oblique light L2 has a lower contrast than the light L1 incident from the normal direction.

In particular, phase plates (first phase plate 30 and second phase plate 32), polarizing plates (first polarizing plate 34 and second polarizing plate 36), a liquid crystal layer 22, and the like. made so that the light intensity in the ON state and the light intensity in the OFF state are optimized, i.e. the luminous intensity in the ON state is large, and the luminous intensity in the OFF state is small relative to the light that enters the liquid crystal display element 20 from the normal direction of the liquid crystal display element 20.

Especially for the luminous intensity in the OFF state, the liquid crystal display element 20 is optically configured such that light that enters the liquid crystal display element 20 from a substantially normal direction of the liquid crystal display element 20 is blocked at a maximum.

Accordingly, the oblique light L2, which does not fall on the liquid crystal display element 20 from the normal direction, is not sufficiently blocked even when the liquid crystal layer 22 is in the OFF state. As a result, the oblique light L2 is emitted at an angle from the liquid crystal display element 20 as light scattering.

However, as described above, L2 that falls from the oblique direction is scattered in the liquid crystal display element 20, and part of the light is emitted in the normal direction (light scattering).

Such scattering of the light flux, in particular, is a serious problem in a liquid crystal display device including a liquid crystal display element capable of realizing high contrast display.

Prism plate

Additionally, the liquid crystal display device must realize not only high contrast display, but also high brightness display.

To satisfy this requirement, a case is provided in which the backlight unit 60 is equipped with a prism plate.

It should be noted that the prism plate is referred to as an optical plate, on the surface of which grooves are provided in this direction so that the direction in which the light transmitted through the prism plate passes is controlled.

The light passing through the prism plate has a certain direction in terms of light intensity.

Therefore, some combinations of a liquid crystal display element and a backlight equipped with a prism plate do not allow a sufficient demonstration of the contrast characteristics of the liquid crystal display element, which leads to lower contrast.

Summary of the invention

It is an object of the present invention to provide a liquid crystal display device capable of realizing high contrast display while instructing the backlight unit to continuously function as a surface light source.

More specifically, it is an object of the present invention to provide a liquid crystal display device capable of suppressing an oblique light force that enters a liquid crystal display element and causes a decrease in contrast.

Another objective of the present invention is to provide a liquid crystal display device capable of realizing a higher contrast display by using a backlight unit comprising a prism plate.

To solve this problem, a liquid crystal display device is proposed, which includes: a liquid crystal display element including a liquid crystal layer, a polarizing plate on the side of incidence of light and a polarizing plate on the side of light exit, and a polarizing plate on the side of light incidence and a polarizing plate on the side light exit is provided on both sides of the liquid crystal layer, respectively; and a backlight module causing light incident through the exit plane of the light to fall on the liquid crystal display element, the backlight module being provided so that light incident from the backlight module on the liquid crystal display element in a diagonal direction that causes light to be emitted from a large the probability from the liquid crystal display element in the normal direction, has a lower luminous intensity than the light incident from the backlight module on the liquid crystal The display item in the other diagonal direction.

Additionally, the liquid crystal display device of the present invention can be arranged such that the backlight includes a light guide plate, a light diffusion plate, and one or more prism plates.

In such an arrangement, it is possible to provide a liquid crystal display device capable of realizing high contrast display while instructing the backlight unit to continuously function as a surface light source. This is explained below.

Liquid crystal element design display

The liquid crystal display element to which light is emitted from the backlight unit is generally configured such that light that enters the liquid crystal display element through the rear surface and from the normal direction and then exits the liquid crystal display element through the front surface and in the normal direction, has maximum contrast. In particular, the optical characteristics of the optical units, such as the polarizing plate and the phase plate and the liquid crystal layer, each of which is included in the liquid crystal display element, are designed so that such light has a high contrast.

Backlight module as a surface light source

On the other hand, it is required that the backlight module must emit light that is uniform in the plane of light output so that a display device that has planar uniform brightness is realized by a liquid crystal display element. In other words, the backlight module is required to have a function such as a surface light source.

In order to function as a surface light source, the backlight module may include a diffusion plate for forcibly scattering light (for example, an upper diffusion plate, a lower diffusion plate or an upper diffusion plate and a lower diffusion plate). With this configuration, for example, the light emitted from the backlight module through the light exit plane of the backlight module is usually oriented in different directions.

Accordingly, the light that leaves the backlight unit and then enters the liquid crystal display element covers not only the light that enters the liquid crystal element from the normal direction of the liquid crystal display element, but also the light that enters the liquid crystal display element from the direction that inclined from the normal direction of the liquid crystal display element.

Contrast reduction

As described above, the contrast of the liquid crystal display element is made with the original data of the light that enters the liquid crystal display element from the normal direction of the liquid crystal display element. Therefore, for example, if the oblique light is scattered in the liquid crystal display element and then is emitted from the liquid crystal display element in the normal direction of the liquid crystal display element, the emitted light does not have the desired brightness (white or black). This is very likely to cause a decrease in contrast.

Additionally, light tilted at the same angle is likely to cause various decreases in contrast according to the directions in which the light is tilted.

The following is an example of such an oblique light. For example, in a liquid crystal display element in which two polarizing plates are provided so that the directions of the absorption axis of the polarizing plates intersect each other at right angles, the light that falls on the liquid crystal display element from a direction inclined to directions parallel to the absorption axes and to directions perpendicular to the absorption axes are less likely to be emitted in the normal direction of the liquid crystal display element.

On the other hand, light that incident on the liquid crystal display element from a direction inclined to directions other than directions parallel to the absorption axes and to directions other than directions perpendicular to the absorption axes is more likely to be emitted in the normal direction of the liquid crystal display element.

Therefore, light that incident on the liquid crystal display element from a direction inclined to directions other than directions parallel to the absorption axes and directions other than directions perpendicular to the absorption axes is more likely to cause a decrease in contrast compared to light that incident on the liquid crystal a display element from a direction inclined to directions parallel to the absorption axes, and to directions perpendicular to the absorption axes.

As described above, the probability of emitting oblique light from the normal direction of the liquid crystal display element is different according to the direction in which the oblique light is tilted.

In this regard, with the above arrangement, the backlight unit is provided so that for incident light from an oblique direction, incident light from a direction that is likely to cause incident light to be emitted from the normal direction of the liquid crystal display element has lower light intensity.

As described above, this configuration results in a liquid crystal display device that allows for higher contrast display while instructing the backlight module to continuously function as a surface light source.

"Direction" is the angle of rotation of the absorption axis, etc. in the plane of the polarizing plate on the falling side, etc., and the counterclockwise direction of the liquid crystal display device when viewed from the light exit side is considered a direct direction.

Further, the liquid crystal display device of the present invention may be configured to further include a reflector film of a polarizer with a brightness enhancement effect provided between the liquid crystal display element and the backlight unit.

With this configuration, despite the film to increase brightness, which can reduce contrast, suppressing the force of oblique light, which is likely to be emitted from the liquid crystal display element in the normal direction, makes it possible to realize high-contrast display.

It should be noted that a reflective polarizing film with a brightness enhancement effect is referred to as a film, which, for example, if the polarized light that reaches the reflective polarizing film with a brightness enhancement includes a P-wave and an S-wave, causes an increase in incident light onto, for example, a polarizing plate adjacent to a reflective polarizing film with a brightness enhancement effect, by forcing one of the polarized waves, such as a P wave, to pass through the film and force reflection of the remaining S-wave on the film.

Further, it is preferable to place the liquid crystal display device of the present invention so that the liquid crystal display element and the backlight unit are provided so as to be close to each other.

Additionally, it is preferable to place the liquid crystal display device of the present invention so that the distance between the liquid crystal display element and the backlight unit is at least 0 mm and not more than 10 mm.

With this arrangement, the liquid crystal display element and the backlight unit are arranged so as to be close to each other, in particular, for example, at a distance of at least 0 mm and not more than 10 mm.

Therefore, despite the fact that a short distance, in particular the absence of a distance between the liquid crystal display element and the backlight module, is likely to increase the decrease in contrast due to oblique light, the above arrangement provides the backlight module in the proper position, making it possible to suppress the decrease in contrast.

Further, the liquid crystal display device of the present invention can be arranged such that a diagonal direction that causes light to be emitted from the liquid crystal display element in a normal direction with a high probability and the prism axis of the prism plate form an angle of not less than 20 ° and not more than 70 ° or not less than 110 ° and not more than 160 °.

It should be noted that the prism plate is referred to as an optical plate, on the surface of which grooves are provided in this direction so that the direction in which the light transmitted through the prism plate passes is controlled. The prism axis indicates the direction of the grooves.

With this arrangement, the diagonal direction that causes light to be emitted most likely from the liquid crystal display element in the normal direction and the prism axis of the prism plate form an angle of not less than 20 ° and not more than 70 ° or an angle of not less than 110 ° and not more than 160 °. This makes it possible to further suppress the decrease in contrast. This is explained below.

Thus, in the case where the backlight module contains a prism plate, the prism plate controls the direction of light transmission, which gives this direction to the strength of the emitted light. In particular, from the light emitted diagonally from the light exit plane of the backlight module, the light tilted in the direction parallel to the prism axis of the prism plate has a higher luminous intensity than the light tilted in the direction perpendicular to the prism axis.

With this arrangement, the direction of the axis of the prism, in which the light emitted diagonally, has a higher light intensity, and the direction of the light, which diagonally falls on the liquid crystal display element and is most likely emitted from it in the normal direction, do not coincide. In particular, these two directions form an angle of not less than 20 ° and not more than 70 ° or an angle of not less than 110 ° and not more than 160 °.

Therefore, the light emitted from the backlight unit is less suitable to act as oblique light, which causes a decrease in contrast.

Therefore, the above arrangement provides a liquid crystal display device having a prism plate provided in the backlight unit for the purpose of increasing the brightness of the liquid crystal display element in the normal direction or to suppress a decrease in contrast.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a linearly polarized vertical alignment liquid crystal display element, and the axis of absorption of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of at least −25 ° and no more than 25 ° or an angle of not less than 65 ° and not more than 115 °.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a linearly polarized vertical alignment liquid crystal display element, and the axis of absorption of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of at least −15 ° and no more than 15 ° or an angle of not less than 75 ° and not more than 105 °.

Further, it is more preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a linearly polarized vertical alignment liquid crystal display element, and the axis of absorption of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of at least -5 ° and not more than 5 ° or an angle of not less than 85 ° and not more than 95 °.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a vertical alignment circularly polarized liquid crystal display element, and the axis of absorption of the polarizing plate on the incidence side and the axis of the prism of the prism plate form an angle of at least −43 ° and no more than 7 ° or an angle of not less than 47 ° and not more than 97 °.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a vertical alignment circular-polarized liquid crystal display element, and the axis of absorption of the polarizing plate on the incidence side and the axis of the prism of the prism plate form an angle of at least −33 ° and not more than -3 ° or angle not less than 57 ° and not more than 87 °.

Further, it is more preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a vertical alignment liquid crystal display element with circular polarization, and the absorption axis of the polarizing plate on the incidence side and the axis of the prism of the prism plate form an angle of at least -23 ° and not more than -13 ° or an angle of not less than 67 ° and not more than 77 °.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a TN liquid crystal display element, and the axis of absorption of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of not less than -25 ° and not more than 25 ° or angle not less than 65 ° and not more than 115 °.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a TN liquid crystal display element, and the axis of absorption of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of not less than -15 ° and not more than 15 ° or angle not less than 75 ° and not more than 105 °.

Additionally, it is more preferable to arrange the liquid crystal display device of the present invention in such a way that the liquid crystal display element is a TN liquid crystal display element, and the axis of absorption of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of not less than -5 ° and not more than 5 ° or an angle of at least 85 ° and not more than 95 °.

In each of the above arrangements, the backlight module is provided in such a way that the absorption axis of the polarizing plate and the axis of the prism of the prism plate form the most suitable angle according to the configurations of the respective liquid crystal display elements.

Therefore, oblique light incident on the liquid crystal display device is less likely to be emitted from the device in its normal direction, providing the possibility of additional effective adjustment of the reduction in contrast.

When the liquid crystal display element has a vertical alignment mode using linear polarization, the liquid crystal display element is generally capable of realizing high contrast display. The above arrangement makes it possible to suppress reduction at such a high contrast.

Additionally, it is preferable to arrange the liquid crystal display device of the present invention in such a way that two prism plates are provided, the prism axes of which intersect each other at right angles.

With this arrangement, two prism plates are provided in such a way that the prism axes of these two prism plates intersect each other at right angles. This enables the liquid crystal display device to emit brighter light in the normal direction of the liquid crystal display device.

Additionally, it is preferable to arrange the liquid crystal device of the present invention so that the light exiting through the light exit plane of the backlight module has a half width of at least 28 ° and not more than 44 °.

Additionally, it is preferable to arrange the liquid crystal device of the present invention in such a way that the half-width is at least 20 ° and not more than 40 °.

Half width

The concept of half-width is explained below. As for the measured model (for example, the backlight module), in which the half-width is measured, the oblique angle at which the light has a luminous intensity that is half of the luminous intensity exiting the measured model through the light exit plane and in the normal direction is referred to as the width half light intensity (in degrees). This is based on such a characteristic that the emitted light has a lower luminous intensity, since the emitted light is more deviated from the normal direction.

With this configuration, the backlight module has a half-width of not more than 44 °, preferably not less than 20 ° and not more than 40 °. This makes it possible to realize a liquid crystal display device capable of performing a higher contrast display while continuously functioning as a surface light source.

In this regard, since the backlight module having the above configuration is configured such that the half width showing the scattering characteristic of the emitted light is set to a corresponding value, the backlight module provides a scattering characteristic of the emitted light sufficient to enable the backlight module to serve as surface light source, while the backlight module suppresses the force of oblique light, which causes a decrease in contrast and. This makes it possible to further suppress the decrease in contrast in the liquid crystal display device.

As described above, the liquid crystal display device of the present invention is configured such that the backlight unit is provided so that light incident from the backlight unit on the liquid crystal display element in the diagonal direction, which is likely to cause light to be emitted from the liquid crystal display element in the normal direction has a lower luminous intensity than light incident from the backlight module on the liquid crystal display element in another gonal direction.

Therefore, the present invention provides a liquid crystal display device capable of implementing a higher contrast display, while constantly instructing the backlight module to continuously function as a surface light source, i.e. a liquid crystal display device capable of suppressing the force of the oblique light that falls on the liquid crystal display element and causes a decrease in contrast.

Brief Description of the Drawings

1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention;

FIG. 2 is a perspective view of a main part of a liquid crystal display device according to an embodiment of the present invention; FIG.

Figure 3 - diagram of a measuring system for measuring the optical characteristics of transmitted light;

4 is a diagram illustrating the relationship between the polar angle and the power of transmitted light;

5 is a diagram illustrating the relationship between the angle of incidence and the power of transmitted light;

6 is a diagram of a measuring system for measuring the optical characteristics of the light emitted from the backlight module;

7 is a diagram illustrating the intensity of light emitted from a backlight module;

Fig. 8 is a diagram illustrating the relationship between the axis of the prism and the light intensity;

9 is a cross-sectional view of a liquid crystal display device, another embodiment of the present invention;

10 is a diagram illustrating the intensity of light emitted from a backlight unit;

11 is a cross-sectional view schematically illustrating a configuration of a model whose half-width, etc. should be measured;

12 is a diagram illustrating the intensity of light emitted from a liquid crystal display element;

13 is a diagram of a difference in light exiting a liquid crystal display device between (i) a liquid crystal display device including a reflective polarizing film with a brightness enhancement effect, and (ii) a liquid crystal display device not including a reflective polarizing film with brightness enhancement effect;

14 is a table illustrating a front contrast of a liquid crystal display device;

15 is a diagram illustrating a light distribution of a backlight unit;

Fig. 16 is a perspective view illustrating a main part of a liquid crystal display device according to an embodiment of the present invention;

FIG. 17 is a perspective view illustrating a main part of a liquid crystal display device; FIG.

Fig. 18 is a perspective view illustrating a main part of a liquid crystal display device of another embodiment of the present invention;

19 is a perspective view illustrating a main part of a liquid crystal display device of yet another embodiment of the present invention.

FIG. 20 is a diagram illustrating light scattering characteristics of respective modes of a liquid crystal display device; FIG.

21 is a diagram illustrating differences between a circularly polarized liquid crystal display device and a linearly polarized liquid crystal display device, each of which has a vertical alignment mode;

Fig is a table showing the azimuthal angles at which oblique light should not fall;

23 is a cross-sectional view schematically illustrating a configuration of a liquid crystal display device;

24 is a cross-sectional view schematically illustrating a configuration of a conventional (known) liquid crystal display device;

25 is a cross-sectional view schematically illustrating a configuration of a conventional (known) liquid crystal display device;

26 is a cross-sectional view schematically illustrating a configuration of a conventional (known) liquid crystal display device.

Description of Embodiments

First Embodiment

An embodiment of the present invention is described below with reference to the drawings.

Liquid crystal display device

The liquid crystal display device 10 of the present invention has a configuration substantially identical to that of the liquid crystal display device 10 already described with reference to FIG. The liquid crystal display device 10 of the present invention is explained below with reference to FIG. 1, which is a cross-sectional view schematically illustrating a liquid crystal display device of the present embodiment.

Namely, the liquid crystal display device 10 of the present invention comprises a liquid crystal display element 20 and a backlight unit 60. The light emitted from the backlight unit 60 through the light exit plane 80 is supplied to the liquid crystal display element 20, whereby a display is performed.

Liquid crystal element display

The liquid crystal display element 20 is explained below. The liquid crystal display element 20 of the present embodiment is configured to have linear polarization of the vertical alignment mode.

Namely, the liquid crystal layer 22, placed between two substrates (not shown), which are located opposite each other, is placed between the first polarizing plate 34, which acts as a polarizing plate on the falling side, and the second polarizing plate 36, which acts as a polarizing plates on the light exit side. The liquid crystal molecules included in the liquid crystal layer 22 have multi-domain alignment (e.g., four-domain alignment) when viewed from above.

Backlight module

The backlight 60 of the present embodiment is explained below. The backlight unit 60 includes a light source (not shown), a light guide plate 64, two diffusion plates (upper diffusion plate 70 and lower diffusion plate 72) and two prism plates (first prismatic plate 66 and a second prismatic plate 68) (see figure 1).

These elements are arranged in layers in the following order: a light guide plate 64, a lower diffuser plate 72, a first prismatic plate 66, a second prismatic plate 68, and an upper diffuser plate 70. It should be noted that, in the present embodiment, the diffuser plate, which has a haze value of 55.0% was used as the upper diffuser plate 70, and the diffuser plate, which has a haze value of 74.5%, was used as the lower diffuser plate 72.

Prism plate

In particular, in the backlight module 60, the first and second prism plates 66 and 68 have, on their respective upper surfaces, linear grooves consisting of triangular maximum points and minimum points (see FIG. 2). Thus, the first and second prism plates 66 and 68 have grooves 67 and grooves 69 on their respective upper surfaces.

The corresponding grooves of the first and second prism plates 66 and 68 are provided so that the directions of the corresponding grooves (arrows P1 and P2 in FIG. 2) intersect each other at right angles.

Direction

A more detailed explanation is given using the azimuthal angle (Φ).

In an almost rectangular shape liquid crystal display device 10, the orthogonal coordinates are composed of long side directions (two-way arrow L in FIG. 2) and short side directions (arrow S in FIG. 2) of the liquid crystal display device 10, and two-way arrow directions L are considered as 0 ° and 180 °, and the directions of the two-sided arrow S are considered as 90 ° and 270 °.

The counterclockwise rotation angle from position 0 (angle from 0 °) is considered the azimuthal angle (Φ).

In this case, the direction P1 of the grooves 67 (groove direction, prism axis) of the first prism plate 66 of the present embodiment has an azimuth angle (Φ) of 90 ° and 270 ° (hereinafter 90 °), and the direction P2 of the grooves 69 of the second prism plate 68 according to the present embodiment, has an azimuth angle (Φ) of 0 and 180 ° (hereinafter 0 °).

Polarizing plate

Next, a direction in which a polarizing plate of the liquid crystal display device 10 is provided is explained.

In the present embodiment, the first polarizing plate 34 is provided in such a way that the direction of its absorption axis (two-sided arrow H1 in FIG. 2) is parallel to the long-side direction L, i.e. the direction in which the azimuthal angle (Φ) is 0 °.

With the liquid crystal layer 22 between the first polarizing plate 34 and the second polarizing plate 36, the second polarizing plate 36 is provided so that the direction of its absorption axis (two-sided arrow H2 in FIG. 2) is parallel to the short-side direction S, i.e. the direction in which the azimuthal angle (Φ) is 90 °.

Thus, two polarizing plates (the first polarizing plate 34 and the second polarizing plate 36) are placed in the so-called ratio of crossed Nicolas prisms so that the absorption axes of these two polarizing plates intersect each other at right angles.

Prism plate and polarizing plate

As explained above, in the present embodiment, the prism plate and the polarizing plate are close to each other, i.e. the second prism plate 68 and the first polarization sheet 34 are configured such that the axis P2 of the prism of the second prism plate 68 and the direction H1 of the absorption axis of the first polarizing plate 34 are opposite with an azimuth angle (Φ) of 0 °, and therefore are parallel to each other .

Thus, the axis P1 of the prism of the first prism plate 66 has an azimuth angle (Φ) of 90 °, the axis P2 of the prism of the second prism plate 68 has an azimuth angle (Φ) of 0 °, the direction H1 of the absorption axis of the first polarizing plate 34 has an azimuth angle (Φ ) at 0 °, and the H2 direction of the absorption axis of the second polarizing plate 36 has an azimuth angle (Φ) of 90 °.

Prism plate

The prism plate is explained in more detail.

In general, it is required that the liquid crystal display device 10 forms a bright display. In particular, it is required that the liquid crystal display device 10 has a high brightness display device for the viewer V viewing the liquid crystal display device 10 from the normal direction.

In order to perform bright display in the normal direction, it is effective to emit light from the backlight unit 60 mainly in the normal direction. Therefore, the prism plate is used to place light emitted from the backlight unit 60 in the normal direction.

A prism plate is an optical plate capable of controlling the direction of passage of light passing through the plate. An example of a prism plate is an optical plate in which grooves are provided in a specific direction.

In the present embodiment, two prism plates 66 and 68 are provided so that the groove directions P1 and P2 (prism axis) intersect each other at right angles. Therefore, in both the short-side direction S and the long-side direction L of the back side of the backlight unit 60, it is possible to place light emitted from the backlight unit 60 in the normal direction.

Therefore, the liquid crystal display device 10 can perform a brighter display.

Contrast

The liquid crystal display device 10 should form not only a bright display, but also a high contrast display. Next, the contrast of the liquid crystal display device 10 is explained.

As explained above, viewer V generally sees a liquid crystal display device 10 from a normal direction. Accordingly, the liquid crystal display element 20 included in the liquid crystal display device 10 is configured to perform high-contrast display in the normal direction. Thus, the liquid crystal display element 20 is configured such that light that enters the rear surface of the liquid crystal display element 20 from the normal direction and is emitted from the front surface of the liquid crystal display element 20 in the normal direction realizes high contrast.

Therefore, oblique light incident on the liquid crystal display element 20 can reduce the contrast.

Such a decrease in contrast due to oblique light is more noticeable in the liquid crystal display device 10, which allows for the implementation of high contrast display and includes a liquid crystal display element with an MVA mode, such as a liquid crystal display element 20.

Decrease in contrast, effect on the panel

Further more specifically, a decrease in contrast due to oblique light is explained.

As described above, the light exiting from the backlight unit 60 passes to the viewer V through two polarizing plates and a liquid crystal layer located between the two polarizing plates.

The following explains the effect of the liquid crystal display panel on light scattering due to oblique light. It should be noted here that the liquid crystal display panel is obtained by excluding two polarizing plates (first and second polarizing plates) from the liquid crystal display element 20. In particular, a liquid crystal display panel is referred to as a liquid crystal panel including a liquid crystal layer 22 that is interposed between two substrates on which a color filter, a switching element, and the like are provided.

Figure 4 shows a diagram illustrating, for two types of measured models (first and second measured models, which are detailed below), the intensity of light transmitted in the normal direction to the surface of the display device of each of the measured models, relative to the oblique light.

Measuring system

Initially, a measuring system for measuring optical characteristics, such as the luminous intensity of transmitted light, etc., is explained below with respect to (a) and (b) of FIG. 3. (a) and (b), where FIG. 3 shows a measuring system for measuring optical characteristics, such as transmitted light power.

As shown in (a) of FIG. 3, in a measurement system for measuring optical characteristics, light is emitted into the measurement model through the rear surface of the measurement model, and light transmitted through the measurement model is received by a light receiving device provided on the front surface of the measurement model, thereby measuring the strength of the received light.

It should be noted here that the oblique angle from the normal direction of the plane of the measured model is referred to as the polar angle (θ) (see (a) of FIG. 3), and the angle of left-side rotation from the lateral direction on the plane is referred to as the azimuthal angle (Φ) (cm . (b) of FIG. 3).

It should be noted that the measuring system allows (i) the inclination of the incident direction of incident light in the direction of the polar angle (θ) and (ii) the rotation of the oblique incident light in the direction of the azimuthal angle (Φ).

On the other hand, the light receiving device is fixed at a polar angle (θ) of 0 ° (azimuthal angle (Φ) of 0 °), i.e. in the normal direction of the plane of the measured model.

It should be noted that the measuring device for performing the measurement as mentioned above is not limited to a specific way. For example, the LCD5200 (product name manufactured by OTSUKA ELECTRONICS CO., LTD) is applicable for such a measurement.

The angle of incidence and the strength of the transmitted light

Next, with reference to FIG. 4, an explanation is provided regarding the transmitted light power with respect to the oblique light in two kinds of measured models (first and second measured models) measured by a measuring system.

The first measured model is obtained by attaching polarizing plates to both sides of the glass substrate, respectively, so that the absorption axes of the corresponding polarizing plates intersect each other at right angles (see "glass + polarizing plates" in Fig. 4). The second measurable model is a liquid crystal display element obtained by attaching polarizing plates to a liquid crystal display panel (see "panel + polarizing plates" of FIG. 4).

Figure 4 shows the relationship between the angle (polar angle (θ)) of the incident light and the transmitted light for these two measured models.

It should be noted that, in each case, “glass + polarizing plates” and “panel + polarizing plates”, two polarizing plates are placed in the ratio of crossed Nicolas prisms, in which the absorption axes of the corresponding two polarizing plates intersect each other at right angles. In particular, the absorption axis of the rear polarizing plate (a polarizing plate located on the side onto which light is incident during the measurement corresponding to the first polarizing plate 34) is oriented in the direction of the azimuth angle (θ) of 0 °. On the other hand, the absorption axis of the front polarizing plate (a polarizing plate located on the side from which light emits during the measurement corresponding to the first polarizing plate 36) is oriented in the direction of the azimuth angle (θ) of 90 °.

On the outside of the polarizing plate on the back side, A-PCF (polarization converting film) (product name manufactured by NITTO DENKO CORPORATION) is additionally provided as a film for increasing brightness.

As is apparent from the transmitted light power in FIG. 4, both of the two measured models (“glass + polarizing plates” and “panel + polarizing plates”) have corresponding lower transmitted light forces, since the incident light is tilted from the normal direction of the respective models.

It should be noted that the power of transmitted light decreases more sharply in the case of “glass + polarizing plates”. In other words, oblique light is more likely to be emitted in the normal direction (polar angle direction (θ) of 0 °) in the case of a “panel + polarizing plate” in which a liquid crystal display panel is added to the “glass + polarizing plate”.

This is probably due to the fact that the light that enters the measured model is very likely to be scattered and change its direction of passage in the liquid crystal display panel. Then, the oblique light changes its direction of passage in the liquid crystal display panel and is emitted in the normal direction of the liquid crystal display panel, which reduces the contrast.

It should be noted that the measurement result illustrated in FIG. 4 is obtained by setting the slope of the incident light in the direction of the azimuthal angle (Φ) to 0 °, i.e. in the direction parallel to the absorption axis of the polarizing plate on the back side.

Dependences of the incident light on θ and Φ

The tendency for oblique light to travel in the normal direction depends, in particular, on the azimuthal angle Φ of oblique light. This trend is explained below with reference to FIG. FIG. 5 is a graph illustrating transmitted light forces for a measured model similar to “panel + polarizing plates” in the event that the polar angle (θ) and the azimuthal angle (Φ) of the incident light change.

The measured model used for the measurement illustrated in FIG. 5 is obtained by attaching polarizing plates to both sides (front and back surfaces) of the liquid crystal display panel in a ratio of crossed Nicolas prisms. It should be noted that the absorption axis of the polarizing plate on the back side (of the polarizing plate located on the side where the light falls during the measurement) is oriented in the direction of the azimuthal angle (Φ) at 0 °, and the absorption axis of the front polarizing plate (polarizing plate located on the side in which light is emitted during the measurement) is oriented in the direction of the azimuthal angle (Φ) of 90 °.

Figure 5 shows that in the range of the polar angle (θ) of 0 ° -70 °, oblique light is emitted in the normal direction at almost all azimuthal angles (Φ). Figure 5 also shows that oblique light is likely to be emitted in the normal direction, in particular at azimuthal angles (Φ) of 45 °, 135 °, 225 ° and 315 °.

Conditions for measuring the strength of transmitted light, etc., for example, a measuring system, correspond to the conditions of the measuring system explained above with respect to (a) and (b) of FIG. 3.

Oblique light behavior

As described above, in the liquid crystal display element 20, the oblique light may change its direction of propagation and be emitted in the normal direction, i.e. towards the viewer V of the liquid crystal display device 10. In addition, oblique light with a high probability behaves differently from light incident from the normal direction, due to the difference in the length of the optical path, etc. while passing through the liquid crystal display element 20. In particular, the light may not be blocked sufficiently, for example, even if the liquid crystal layer 22 is in the OFF state (the OFF state of the liquid crystal layer 22 is referred to as a state in which the black image is displayed by the liquid crystal display element, i.e. the state in which the crystalline display element has the lowest transmittance).

As a result, it often happens that oblique light is emitted as scattering of the light flux in the normal direction, reaching the viewer's eye V.

Accordingly, in order to realize high contrast, oblique light is less likely to be emitted in the normal direction.

For a more effective increase in contrast (to prevent a decrease in contrast), it is effective to prevent light from falling from directions whose azimuthal angles are 45 °, 135 °, 225 ° and 315 °. This is due to the fact that light incident from such directions is very likely to cause scattering of the light flux.

Prism axis and output light power

In this regard, the liquid crystal display device 10 of the present embodiment is configured such that the groove direction (prism axis) of the prism plate and the direction of the absorption axis of the polarizing plate are parallel to each other or perpendicular to each other, thereby preventing a decrease in contrast. This is explained below.

Figures 7a and 7b show the relationship between the axis of the prism (direction of the groove of the prism plate) and the intensity of the light emitted from the backlight unit 60.

In particular, the intensity of the light emitted from the backlight unit 60 is measured at all azimuthal angles (Φ) and at polar angles (θ) from 0 ° to 88 °.

Measuring system and model for measuring

The measuring system for measuring the intensity of the light emitted from the backlight unit 60 may be, for example, the measuring system illustrated in FIG.

In particular, the measurement can be performed using a viewing angle measuring device (EZContrast XL88: manufactured by ELDIM). Such a measuring device can measure all azimuthal angles (Φ) and polar angles (θ) from 0 ° to 88 ° together in a short time.

The measurement results shown in (a) and (b) of FIG. 7 are obtained by the above viewing angle measuring device.

The definitions of the azimuthal angle (Φ) and polar angle (θ) are identical to the definitions already explained above.

The following explains the configurations of the measured models used in the measurements shown in figa, b.

The measurement model used in the measurement shown in FIG. 7a is referred to as backlight module A, and the measurement model used in the measurement shown in FIG. 7b is referred to as backlight module B. The configurations of the backlight modules A and B are identical to those of the backlight module 60 shown in FIG.

Thus, each of the backlight modules A and B is configured such that two prism plates (first prism plate 66 and second prism plate 68) are provided so that groove directions P1 and P2 (prism axis) for grooves 67 and 69 of the two prism plates, respectively, intersect each other at right angles.

The backlight module A is configured such that the prism axis P1 of the first prism plate 66 has an azimuth angle (Φ) of 0 °, and the prism axis P2 of the second prism plate 68 has an azimuth angle (Φ) of 90 °.

In contrast, the backlight unit B is configured such that the prism axis P1 of the first prism plate 66 has an azimuth angle (Φ) of 45 °, and the prism axis P2 of the second prism plate 68 has an azimuth angle (Φ) of 135 °.

Thus, the backlight modules A and B differ from each other in terms of the directions of their orthogonal prism axes.

Measurement result

Next, the measurement results in relation to (a) and (b) of FIG. 7a, b in FIG. 8 are explained.

As shown in FIG. 7a, in the measured model (backlight module A), in which the prism axes are positioned at azimuthal angles (Φ) of 0 ° and 90 °, respectively, light emitted diagonally (light emitted at a polar angle ( θ)), has a higher luminous intensity at azimuthal angles (Φ) at 0 ° and 180 ° and at azimuthal angles (Φ) at 90 ° and 270 °.

Additionally, as shown in FIG. 7b, in the measured model (backlight module B), in which the prism axes are placed at azimuthal angles (Φ) of 45 ° and 135 °, respectively, the light emitted diagonally has a higher luminous intensity at azimuthal angles (Φ) at 45 ° and 225 ° and at azimuthal angles (Φ) at 135 ° and 315 °.

Based on the measurement results shown in figa, b, the ratio between the direction (orientation) of the axis of the prism of the backlight module 60 and the power of the emitted light is such that the light is most likely to be emitted at a polar angle (θ) in the direction of the azimuthal angle (Φ ) parallel to the direction of the axis of the prism.

Additionally, FIGS. 8a, b show how the power distribution of the emitted light, the measurement results of which are shown in FIGS. 7a, b, depend on the polar angles (θ) in the directions in which the azimuthal angles (Φ) are 0 ° and 45 ° , respectively.

Fig. 8a shows a measurement result corresponding to that shown in Fig. 7a, and Fig. 8b corresponds to the measurement result shown in Fig. 7b.

As shown in FIG. 8a, the intensity of the light emitted from the backlight unit A is higher when the polar angle (θ) exists in the direction in which the azimuthal angle (Φ) is 0 ° than when the polar angle (θ) exists in the direction in which the azimuthal angle (Φ) is 45 °.

As shown in FIG. 8b, the intensity of the light emitted from the backlight unit B is higher when the polar angle (θ) exists in the direction in which the azimuthal angle (Φ) is 45 ° than when the polar angle (θ) exists in the direction in which the azimuthal angle (Φ) is 0 °.

As described above, in the backlight unit A, the axis has azimuthal angles (Φ) of 0 ° and 90 °, and accordingly, it is found that the emitted light has a higher luminous intensity in a direction parallel to the axis of the prism.

Similarly, in the backlight module B, the axis has azimuthal angles (Φ) of 45 ° and 135 °, and accordingly, the emitted light has a higher luminous intensity in the direction parallel to the prism axis, as in the case of the backlight module A .

Prism axis and absorption axis

In the liquid crystal display device 10 of the present embodiment, as shown in FIG. 2, explained above, the prism axis of the prism plate and the absorption axis of the polarizing plate are parallel to each other or perpendicular to each other. Accordingly, a decrease in contrast is less likely. This is explained below.

As described above, in the liquid crystal display element 10 of the present embodiment shown in FIG. 2, the prism axis P1 of the first prism plate 66 has an azimuth angle (Φ) of 90 °, the prism axis P2 of the second prism plate 68 has an azimuth angle (Φ) of 0 °, the direction H1 of the absorption axis of the first polarizing plate 34 has an azimuth angle (Φ) of 0 °, and the direction H2 of the absorption axis of the first polarizing plate 36 has an azimuth angle (Φ) of 90 °.

The transmission characteristic of the liquid crystal display element

As explained above with reference to FIG. 5, in two polarizing plates in which the absorption axes are located in the ratio of crossed Nicolas prisms, i.e. at azimuthal angles (Φ) of 0 ° and 90 °, respectively, oblique light incident at azimuthal angles of 45 °, 135 °, 225 ° and 315 ° is most likely to be emitted in the normal direction.

In contrast, oblique light incident at azimuthal angles of 0 °, 90 °, 180 ° and 270 ° is relatively less likely to be emitted in the normal direction.

Angle distribution of light emitted from a backlight module

The following explains the distribution of the angles of the light emitted from the backlight module. The distribution of the angles is obtained by illustrating the intensity of the light emitted from the backlight module at an azimuth angle of 0 ° to 360 ° and a polar angle (θ) of 0 ° to 88 °.

As explained above with respect to FIG. 7a, etc., in the case of the backlight unit 60 in which two prism plates are arranged such that the prism axes of these two prism plates have azimuthal angles (Φ) of 90 ° and 0 °, accordingly, the light tilted at azimuthal angles (Φ) of 0 °, 90 °, 180 ° and 270 ° is most likely to be emitted from the backlight unit 60.

Accordingly, in the liquid crystal display device 10 of the present embodiment, the azimuthal angles (Φ) at which light is most likely emitted diagonally from the backlight unit 60 (0 °, 90 °, 180 ° and 270 °) do not coincide with the azimuthal angles (Φ), at which light incident diagonally on the liquid crystal display element 20 and is likely to be emitted from it in its normal direction (45 °, 135 °, 225 °, 315 °), and coincide with azimuthal angles (Φ), at which light falls diagonally on the liquid crystal The display element 20 is less likely to be emitted from it in the normal direction (0 °, 90 °, 180 ° and 270 °).

Accordingly, it is possible to suppress the luminous intensity which is incident diagonally on the liquid crystal display element 20 and then emitted from it in the normal direction.

Therefore, it is possible to suppress a decrease in contrast while maintaining brightness in the normal direction by using a prism plate.

Flat uniformity and semi width

Next, planar uniformity and half-width of the backlight unit 60 are explained.

First of all, the liquid crystal display device 10 is preferably configured such that light that is uniformly bright in the plane of the backlight unit 60 exits the backlight unit 60 so that a display that is uniformly bright in the plane of the liquid crystal display device 10 is realized. Namely, the backlight unit 60 is preferably a uniform surface light source.

In order to realize such a characteristic, the light exiting from the backlight unit 60 must have a high scattering ability. In order to realize such a scattering characteristic, one possible option is to provide a backlight unit 60 with a scattering plate (upper scattering plate or lower scattering plate or upper scattering plate and lower scattering plate) having a high scattering ability.

Semi width

Next, the half-width of the backlight unit 60 is explained.

The backlight unit 60 of the present embodiment has a half-width of 31 °. This is explained below.

Measuring system

The half-width measurement can be performed by using a measuring system to measure the intensity of the light emitted from the backlight unit 60.

Thus, as illustrated in FIG. 6, in a measuring system for measuring half-width, the light intensity emitted from the measured models is measured with respect to all azimuthal angles and all polar angles. Then, based on the measurement, the half-width is determined, which is the oblique angle at which the light emitted in a particular direction has a luminous intensity that is half of the light emitted in the normal direction of the measured model.

Namely, the angle is determined at which the light emitted in the oblique direction has a luminous intensity that is half of the light emitted in the normal direction.

It should be noted that the measuring device for performing the measurement as mentioned above is not limited to a specific way. For example, EZContrast 88 (product name manufactured by ELDIM) is applicable for such a measurement.

The backlight unit 60 acts as a measured model, thereby measuring the half-width of the backlight unit 60.

The azimuthal angle (Φ) and polar angle (θ) assignments are described above. For example, the polar angle (θ) indicates the angle of inclination from the normal direction of the surface (light exit plane 80) of the backlight unit 60 serving as the measured model. The azimuthal angle (Φ) indicates the angle of rotation counterclockwise from the horizontal direction (right to left direction, lateral direction) on the plane of the measured model.

Top diffuser plate

It should be noted here that in the present embodiment, the diffuser plate, in which the light exiting from the backlight unit 60, has a half-width of 31 °, is used for the upper diffuser plate 70. The following description explains this aspect.

The half-width is measured for the backlight module 60, which is schematically illustrated in FIG. 1 and acts as the measured model. In particular, the received light power is measured in a state in which the light guide plate 64, the lower diffusion plate 72, the first prism plate 66, the second prism plate 68 and the upper diffusion plate 70 are arranged in layers in this order.

The azimuthal angle (Φ) at which light is incident is set in the range from 0 ° to 360 ° and the average of eight half-widths observed every 45 ° relative to the azimuthal angle (Φ) in the range is calculated (the average is hereinafter referred to as "half-width (0 ° - 360 °) ").

It should be noted that in the present embodiment, a diffusion plate, which has a haze value of 55.0%, is used for the upper diffusion plate 70, and a diffusion plate, which has a haze value of 74.5%, is used for the lower diffusion plate 72.

The liquid crystal display device 10 of the present embodiment is configured to have a half width of 31 °.

Therefore, it is possible to suppress the power of light incident diagonally on the liquid crystal display element 20. This makes it possible to suppress a decrease in contrast.

This enables the liquid crystal display device 20 to have high contrast.

"Moire" formed due to the interaction between two different periodic patterns, i.e. between the periodic pixel pitch pattern of the liquid crystal display element 20 and the periodic groove pitch pattern of the prism plate can be adjusted by providing a diffusion plate (upper diffuser plate or lower diffuser plate or upper diffuser plate and lower diffuser plate) between the prism plate and the liquid crystal display element 20.

Further, in the liquid crystal display device 10 of the present embodiment, the liquid crystal display element 20 and the backlight unit 60 are arranged so as to be close to each other. In particular, the distance between the liquid crystal display element and the backlight unit is about 1 mm.

Therefore, although such a close proximity is likely to increase the decrease in contrast due to oblique light, it is possible to suppress the decrease in contrast.

The liquid crystal display element 20 and the backlight module 60 may be provided so as to be attached to each other (distance is 0 mm).

Second Embodiment

Another embodiment of the present invention is explained below with reference to Fig.9 and further. It should be noted that a configuration that is not described in the present embodiment is identical to the configuration described in the first embodiment.

The liquid crystal display device 10 of the present embodiment is configured to further include a reflective polarizing film with a brightness enhancement effect 40 compared to the configuration of the liquid crystal display device 10 of the first embodiment.

Namely, as illustrated in FIG. 9, which is a cross-sectional view schematically illustrating a liquid crystal display device 10 of the present embodiment, the liquid crystal display device 10 of the present embodiment further includes A-PCF (polarization converting film) (title a product manufactured by NITTO DENKO CORPORATION) as a reflective polarizing film with an effect of 40 increasing brightness between (i) the first polarizing plate 34 of two polarizing plates (first polarizing plate 34 and second polarizing plate 36), which is closer to the backlight module 60, and (ii) the backlight module 60.

Reflective Polarizing Film with Brightening Effect

It should be noted here that a reflective polarizing film with a brightness enhancement effect 40 is referred to as a film in which, for example, a mechanism, as described below, causes an increase in the light that enters the polarizing plate adjacent to the film.

The mechanism for this is as follows. For example, if the polarized light that reaches the reflective polarizing film with the brightness enhancement effect 40 includes the P wave and the S wave, the reflective polarizing film with the brightness enhancement effect 40 causes (i) the passage of only one of the polarized waves, such as a P-wave, through itself and (ii) reflection of the remaining S-wave from itself. When the reflected S-wave is scattered and reflected by the backlight unit 60 and again reaches the reflective polarizing film with the brightness enhancement effect 40, the S-wave thus reflected partially changes to the P-wave. Then, a reflective polarizing film with a brightness enhancement effect 40 causes the P-wave, thus changed, to pass through itself. Such an operation is repeatedly performed, so that only the P-wave, for example, selectively passes through a reflective polarizing film with an effect 40 of increasing brightness.

It should be noted that a reflective polarizing film with a brightness enhancement effect 40 is not limited to A-PCF (product name). For example, D-BEF (product name: short for “Brightening Film” manufactured by Sumitomo 3M Limited) may also apply. It should also be noted that this reflective polarizing film with a brightness enhancement effect may be referred to as a reflective film for polarized light or a mirror film for polarized light.

Reflective Polarizing Film with Brightening Effect and Radiated Light

Initially, with reference to FIGS. 10a, b, the following description explains the difference in the intensity of the light exiting the backlight unit 60 between (i) a case where a reflective polarizing film 40 with a brightness enhancement effect is provided, and (ii) a case when reflective polarizing film 40 with the effect of increasing the brightness is not provided.

10a, b are diagrams illustrating the intensity of light exiting from the backlight unit 60.

In particular, in FIG. 10a, the backlight module 60 (see FIG. 1), i.e. a laminated product of a light guide plate 64, a lower diffusion plate 72, a first prism plate 66, a second prism plate 68 and an upper diffusion plate 70 serves as a measurement model. Figure 10a shows the dependence of the light exiting from the light exit plane 80 of the measured model in the normal direction on the azimuthal angle (Φ) and the polar angle (θ).

In contrast, in FIG. 10b, a measurable model is obtained by using A-PCF serving as a reflective polarizing film 40 with a brightness enhancement effect on the measurable model. Figure 10 shows the dependence of the light leaving the measured model in the normal direction on the azimuthal angle (Φ) and the polar angle (θ) (similar to Fig. 10a).

On figa, b schematically shows the configuration of the layers of the modules 60 backlight used in the measurements illustrated in figa, b, respectively.

11a, b are cross-sectional views schematically illustrating layer configurations of backlight modules 60. The measurement result illustrated in FIG. 10a is obtained relative to the backlight module 60, the configuration of which is shown in cross section in FIG. 11a. Similarly, the measurement result illustrated in FIG. 10b is obtained with respect to the backlight unit 60, the configuration of which is shown in cross section in FIG. 11b (this backlight unit 60 includes a reflective polarizing film 40 with a brightness enhancement effect).

It should be noted that conditions such as a measuring system for measuring light intensities correspond to a measuring system or the like described with reference to FIG. 6.

As illustrated in FIGS. 10a, b, when the backlight unit 60 comprises a reflective polarizing film 40 with a brightness enhancement effect, in other words, when the backlight module 60 is configured so that light is transmitted through the reflective polarizing film 40 with a brightness enhancement effect, is provided a wider range of oblique light that is emitted diagonally from the backlight unit 60 to the liquid crystal display element 20 and is emitted from it in its normal direction.

Namely, in the case of the backlight unit 60 including the reflective polarizing film 40 with the brightness enhancement effect, light is emitted from the light exit plane 80 of the backlight unit 60 in a wide range of polar angles (θ) in the range of almost all azimuthal angles (Φ) .

The extension of the range of light emitted from the backlight unit 60, if a reflective polarizing film 40 with a brightness enhancement effect is provided, is significant, in particular in the range of oblique angle (polar angle (θ)) from 30 ° to 70 °.

According to the above description, in the case where a reflective polarizing film 40 with a brightness enhancement effect is provided between (i) a backlight unit 60 and (ii) a first polarizing plate 34 (a polarizing plate closer to the backlight module 60) of the liquid crystal display element 20, a larger amount of oblique light enters the liquid crystal display element 20.

Light coming out of a liquid crystal device display

Further, the following description explains how the light exiting from the liquid crystal display element 20 in the normal direction depends on the azimuthal angle (Φ) and the polar angle (θ) of the incident light of Fig. 12 (a, b).

It should be noted here that in FIG. 12a, the liquid crystal element 20 according to the first embodiment, the configuration of which is schematically illustrated in FIG. 1, serves as a measurement model, and light intensities are measured in the normal direction.

In contrast, in FIG. 12b, the liquid crystal display element 20 of the present embodiment, the configuration of which is schematically illustrated in FIG. 9 (obtained by modifying the liquid crystal display element 20 of the first embodiment so as to further include an A-PCF serving as reflective polarizing film 40 with the effect of increasing brightness), serves as the measured model.

12a, b illustrate the difference between (i) a liquid crystal display element 20 including a reflective polarizing film 40 with a brightness enhancement effect, and (ii) a liquid crystal display element 20 that does not include a reflective polarizing film 40 with an effect increase the brightness, from the point of view of the dependence of the light exiting the liquid crystal display element 20 in the normal direction from the azimuthal angle (Φ) and the polar angle (θ) of the incident light.

It should be noted that conditions such as a measuring system for measuring the received light forces correspond to a measuring system or the like described with reference to FIGS. 3a, b.

12a, b, a liquid crystal display element 20 including a reflective polarizing film 40 with a brightness enhancement effect is more likely to emit light incident at azimuthal angles (Φ) of 45 °, 135 °, 225 °, and 315 ° and at polar angles (θ), in particular 30 ° -70 °, in the normal direction.

13 is a diagram illustrating a difference between (i) a liquid crystal display element 20 including a reflective polarizing film 40 with a brightness enhancement effect, and (ii) a liquid crystal display element 20 that does not include a reflective polarizing film 40 with an effect increase the brightness in the light exiting from the liquid crystal display element 20 in the normal direction (subtracting under similar conditions the light output from the liquid crystal display element 20, incl including a reflective polarizing film 40 with a brightness enhancement effect, from a luminous intensity exiting from a liquid crystal display element 20 that does not include a reflective polarizing film 40 with a brightness enhancement effect).

As illustrated in FIG. 13, a liquid crystal display element 20 including a reflective polarizing film 40 with a brightness enhancement effect is more likely to cause incident light to be emitted at azimuthal angles (Φ) of 45 °, 135 °, 225 ° and 315 °, and at a polar angle (θ) of 50 °, in particular in the normal direction.

As described above, the emission of such oblique light in the normal direction of the liquid crystal display element 20 tends to cause a decrease in contrast.

It should be noted that the measurement systems and the measured models for finding the difference in the radiation intensity for the measurement illustrated in FIG. 13 correspond to those described previously. It should also be noted that this measurement is performed relative to the liquid crystal display element 20, which performs the display of a black image.

A liquid crystal display device of the present embodiment

As described above, when a reflective polarizing film 40 with a brightness enhancement effect is provided between the backlight unit 60 and the liquid crystal display element 20, the intensity of light incident diagonally on the liquid crystal display element 20 (light incident on the liquid crystal display element 20 in a direction that it most likely causes light to be emitted from the liquid crystal display element 20 in the normal direction), becomes greater than the intensity of the light incident on the liquid crystal The thallic display element 20 is in the normal direction, which leads to a decrease in contrast.

Accordingly, in order to control the decrease in contrast, it is necessary to reduce a large amount of oblique light when a reflective polarizing film 40 with a brightness enhancement effect is provided than when a reflective polarizing film 40 with a brightness enhancement effect is not provided.

In this regard, the liquid crystal display device 10 of the present embodiment is configured to adjust the amount of light that is emitted from the backlight unit 60 and falls onto the liquid crystal display element 20 at an angle that is likely to cause light to be emitted from the liquid crystal display element 20 in the normal direction . In particular, the liquid crystal display device 10 of the present embodiment is configured to control the light intensity characteristic in the direction of the azimuthal angle of the backlight unit 60.

Using the equations, the above is expressed as follows: the total power S of the light passing through the liquid crystal display element in the normal direction is represented by the following equation

уравнение (1)S = ∫∫ L (θ, Φ); T (θ, Φ) sin θ d θ d Φ ...

equation (1)

where: L (θ, Φ) represents a characteristic of the light intensity emitted from the backlight unit 60 (the characteristic shown in FIGS. 7 and 10); T (θ, Φ) represents the light transmittance with respect to the normal direction of the liquid crystal display element when light is incident on the liquid crystal display element diagonally with a diagonal direction (θ, Φ); θ - represents the polar angle, Φ - represents the azimuthal angle.

According to the present invention, the total luminous intensity S is reduced by controlling L (θ, Φ) in equation (1).

Next, with reference to Fig. 14, an effect of increasing contrast in accordance with the present invention is explained. On Fig shows the front contrast of the liquid crystal display device. On Fig shows the distribution of the light intensity of the backlight module corresponding to Fig.14.

On Fig shows the results of measuring the front contrast, provided that the A-PCF (called PCF on Fig and 15) is provided or not provided, provided that the axis angle of the prism plate is (0 ° -180 °, 90 ° - 270 °) or (45 ° -225 °, 135 ° -315 °), and provided that the haze value of the upper scattering plate is 32.5%, 55%, 76% or 81.4%. In the measurement, a liquid crystal display element of the VA mode using linear polarization was used, and the absorption axes of the first and second polarizing plates were set to 0 ° and 90 °, respectively.

The underlined numbers from the contrast values shown in FIG. 14 indicate that the contrast values increase when the angles of the prism plate axis change from (45 ° -225 °, 135 ° -315 °) to (0 ° -180 °, 90 ° - 270 °).

Thus, if A-PCF is not provided when the diffuser plate has a haze value of 55% and 76%, the contrast value is increased by changing the axis angle of the prism plate. In contrast, if A-PCF is provided when the diffuser plate has a haze value of 32.5%, the contrast value is increased.

In case A-PCF is not provided when the upper diffuser plate has a higher haze value (for example, 81.4%), the dependence on the Φ of the characteristic L (θ, Φ) of the light intensity emitted from the backlight module (i.e. directivity to the direction of the azimuthal angle decreases, and the light intensity L relative to 0 does not significantly change regardless of the azimuthal angle Φ). Therefore, the change in the contrast value when the prism plate axis angle is changed is small. Further, in the case where an A-PCF is provided, the A-PCF makes the dependence of the light intensity characteristic L (θ, Φ) on Φ small. Therefore, the degree of increase in contrast due to a change in the angle of the axis of the prism plate is less compared to the case when A-PCF is not provided.

Configuration Examples

Examples of configurations of a liquid crystal display device 10 of the present invention will be specifically explained below with reference to the drawings.

On Fig shows a General view of an example of a liquid crystal display device (linearly polarized VA mode) 10. As shown in Fig.16, the liquid crystal display element 10 of the present embodiment is made so that the axis P1 of the prism of the first prism plate 66 has an azimuth angle (Φ) at 90 °, the prism axis P2 of the second prism plate 68 has an azimuthal angle (Φ) of 0 °, the H1 direction of the absorption axis of the first polarizing plate 34 has an azimuthal angle (Φ) of 0 °, and the H2 direction of the absorption axis of the second polarizing ins 36 is in the azimuth angle (Φ) of 90 °.

Therefore, it is possible to suppress the intensity of the light emitted from the backlight unit 60, in particular in the direction of the polar angle (θ) of approximately 50 ° with an azimuth angle (Φ) of 45 °, 135 °, 225 ° and 315 °, which is large the probability leads to lower contrast due to the light incident on the liquid crystal display element 20 at an azimuthal angle through the reflective polarizing film 40 with the effect of increasing brightness.

Therefore, it is possible to suppress the decrease in contrast due to the emission of such oblique light from the liquid crystal display element 20 in the normal direction. In particular, compared with the configuration in which the direction in which the emitted light is high according to the dependence of the light emitted from the backlight unit 60 on the angle (azimuth angle (Φ) and polar angle (θ)) is identical to the direction in which light incident diagonally on the liquid crystal display element 20 is most likely to be emitted in the normal direction (low contrast configuration), the liquid crystal display device 10 of the present embodiment, showing Noah, 16, makes it possible to enhance the contrast of approximately 3-4%.

The low contrast configuration here indicates a configuration, for example, shown in FIG. 17 is a cross-sectional view schematically showing a configuration of a liquid crystal display device 10.

An example of such a configuration (low contrast configuration) is a configuration in which the prism axis of the prism plate and the absorption axis of the polarizing plate form an angle of 45 ° or 135 °.

In particular, as shown in FIG. 17, an example of such a configuration is a configuration in which the prism axis P1 of the first prism plate 66 has an azimuth angle (Φ) of 45 °, the prism axis P2 of the second prism plate 68 has an azimuth angle (Φ) of 135 °, the direction H1 of the absorption axis of the first polarizing plate 34 has an azimuth angle (Φ) of 0 °, and the direction H2 of the absorption axis of the second polarizing plate 36 has an azimuth angle (Φ) of 90 °.

Other configuration

The present invention is not limited to the description of the above embodiments, but may be varied by those skilled in the art within the scope of the claims. An embodiment based on an appropriate combination of hardware disclosed in various embodiments is included within the scope of the present invention.

Prism axis and absorption axis

For example, the above configuration of the direction of the prism axis of the prism plate and the direction of the absorption axis of the polarizing plate is such that the axis P1 of the prism of the first prism plate 66 has an azimuth angle (Φ) of 90 °, the axis P2 of the prism of the second prism plate 68 has an azimuth angle (Φ) of 0 °, the direction H1 of the absorption axis of the first polarizing plate 34 has an azimuth angle (Φ) of 0 °, and the direction H2 of the absorption axis of the second polarizing plate 36 has an azimuth angle (Φ) of 90 °, as shown in FIG. 16.

The configuration of the present invention is not limited to the above configuration, for example, that the prism and P2 axes P1 rotate through an azimuth angle (Φ) of 90 °.

Thus, as shown in FIG. 18, which is a diagram schematically showing the main part of the liquid crystal display device 10 according to the present invention, the configuration of the present invention can be such that the prism axis P1 of the first prism plate 66 has an azimuth angle (Φ) of 0 ° , the axis P2 of the prism of the second prism plate 68 has an azimuthal angle (Φ) of 90 °, the direction H1 of the absorption axis of the first polarizing plate 34 has an azimuthal angle (Φ) of 0 °, and the direction H2 of the axis of absorption of the second polarizing plate 36 is in the azimuth angle (Φ) of 90 °.

Further, as shown in FIG. 19, which is a diagram schematically showing a main part of the liquid crystal display device 10 of the present invention, the configuration of the present invention may be such that the prism axis P1 of the first prism plate 66 has an azimuth angle (Φ) of 45 °, the axis The P2 prisms of the second prism plate 68 have an azimuthal angle (Φ) of 135 °, the direction H1 of the absorption axis of the first polarizing plate 34 has an azimuthal angle (Φ) of 135 °, and the direction H2 of the absorption axis of the second polarizing plate 36 has t azimuth angle (Φ) of 45 °.

In the configuration shown in FIG. 19, the direction H2 of the absorption axis of the second polarizing plate 36 closer to the viewer V of the liquid crystal display device 10 is not the so-called axis direction, such as the azimuthal angle (Φ) of 0 ° or 90 °, but tilted relative to the direction axis.

Therefore, even when the viewer V of the liquid crystal display device 10 wears polarized sunglasses 90, the image displayed by the liquid crystal display device 10 is not completely blocked by the polarized sunglasses 90.

Thus, if viewer V wears polarized sunglasses 90, if the absorption axis of polarized sunglasses 90 and the direction H2 of the absorption axis of the second polarizing plate 36 intersect each other at right angles, viewer V cannot see the image displayed by the liquid crystal display device 10 .

Often there is the fact that the axis of absorption of polarized sunglasses 90 is in the direction of G1 or G2 with two arrows. Thus, it often happens that the absorption axis of the polarized sunglasses 90 is located in the vertical direction G1 or the horizontal direction G2 when the viewer V is wearing polarized sunglasses 90.

In this regard, as shown in FIG. 19, when the direction H2 of the absorption axis of the second polarizing plate 36 is in the direction in which the azimuthal angle (Φ) is 45 °, even if the absorption axis of the polarized sunglasses 90 is in the vertical direction G1 or horizontal direction G2, viewer V does not experience such a problem that the image displayed by the liquid crystal display device 10 may be completely invisible.

LCD display mode

The above description explains the linear polarization of the vertical alignment mode. The mode of the liquid crystal display device of the present invention is not limited to this. Of the liquid crystal display devices with the vertical alignment mode, the so-called type with circular polarization is also applicable. Circular polarization is made so that: liquid crystal molecules are not subjected to multi-domain alignment, but are omnidirectionally aligned using rivets, etc .; and phase plates, such as λ / 4 plates, are provided between the liquid crystal layer and the corresponding polarizing plates. It should be noted that the differences between the above linear polarization and circular polarization are described below with reference to Fig.21.

It should be noted that the present invention is also applicable, for example, in TN (twist-nematic) mode and IPS (planar switching) mode, as well as vertical alignment mode.

It should be noted here that the oblique light scattering characteristics of the above modes of the liquid crystal display device are explained below with reference to (a) to (e) of FIG.

20a-e are diagrams illustrating light scattering characteristics of respective modes of a liquid crystal display device. The following description specifically explains this aspect.

20a-e illustrate the dependences of the intensities of light emerging from the normal direction in the measured models on the direction of incidence (azimuth angle (Φ) and polar angle (θ)). The measured model in FIG. 20a includes polarizing plates that are provided on both sides of the glass substrate so that their respective optical axes intersect each other at right angles (in the ratio of crossed Nicolas prisms). The measured model in FIG. 20b has circular polarization (already described) of a liquid crystal display element with a vertical alignment mode. The measured model in FIG. 20c includes a liquid crystal display element using the IPS mode. The measured model in FIG. 20d includes a liquid crystal display element using the TN mode. The measurement model in FIG. 20e is a linear polarization vertical alignment liquid crystal display element described in the above-described embodiments.

As illustrated in FIGS. 20a-e, oblique light is more likely to be emitted in the normal direction in the measured models including the liquid crystal layers of FIG. 20b-e compared to the measured model, which does not include the liquid crystal layer, but includes only a glass substrate and polarizing plates (see (A) in FIG. 20a).

Accordingly, as described above, controlling the direction of the light exiting from the backlight can prevent a decrease in contrast.

Additionally, as illustrated in FIG. 20e, oblique light is more likely to be emitted in the normal direction with linear polarization of the vertical alignment mode. As a result, the effect of the present invention to prevent a decrease in contrast is more significant with linear polarization.

It should be noted here that circular polarization and linear polarization are explained below with reference to FIG. 21, illustrating the difference between the two types of vertical alignment modes.

As illustrated in FIG. 21, liquid crystals (liquid crystal molecules) of the liquid crystal layer are omnidirectionally aligned with centering around a protrusion, such as a rivet, in the type of circular polarization of the vertical alignment mode.

In contrast, the liquid crystal layer is divided into a plurality of alignment regions R when viewed from above in linear polarization of the vertical alignment mode. It should be noted here that the alignment region is referred to as the region in which the liquid crystals (liquid crystal molecules) are aligned in a direction different from the direction in which the liquid crystals (liquid crystal molecules) of the portion adjacent to the region are aligned. 21 illustrates an example of four-domain alignment.

Circular polarization and linear polarization differ in the configuration of the layer of the liquid crystal display element in accordance with the difference in the configuration of the liquid crystal layer. Namely, with linear polarization, only polarizing plates are provided on both sides of the liquid crystal layer, respectively. In contrast, in circular polarization, phase plates such as λ / 4 plates (circular polarizing plates) are provided in addition to polarizing plates on both sides of the liquid crystal layer (liquid crystal panel), respectively.

In particular, for example, phase plates are provided on both sides of the liquid crystal layer, respectively, and then polarizing plates are provided on the outer sides of the respective phase plates.

The linear polarization of the vertical alignment mode, in general, has a higher contrast than the circular polarization of the vertical alignment mode. As a result, the backlight of the present invention functions more efficiently with linear polarization than with circular polarization.

It should be noted that the measurement conditions, such as the measuring system used in the measurement of luminous intensity, the results of which are shown in figa-e, are similar to the conditions described previously with reference to figa and b, etc.

Next, with reference to FIG. 22, showing configurations, etc. polarizing plates of individual modes of liquid crystals, the azimuthal angle is explained at which oblique light should not fall in individual modes of operation of liquid crystals.

Fig. 22 shows typical examples of polarizing plate positions and azimuthal angles determined based on the scattering characteristics drawing as azimuthal angles at which oblique light should not fall, with respect to each of the liquid crystal modes explained above with respect to Fig.20b-d.

In the VA mode using linear polarization and the TN mode, the azimuth angle (Φ), in which oblique light should not fall, is 45 ° from the absorption axis of the polarizing plate. However, the preferred angle of the absorption axis of the polarizing plate is different between the VA mode using linear polarization and the TN mode.

In contrast, in the VA mode using circular polarization, the azimuthal angle (Φ), in which oblique light should not fall, is not 45 ° from the absorption axis of the polarizing plate, but 0, 180, 90 and 270 °, in particular 0 ° and 180 °, if the absorption axis of the polarizing plate on the rear side (first polarizing plate 34) is located at 63 °, and the absorption axis of the polarizing plate on the front side (second polarizing plate 36) is located at -27 °.

Additionally, in the IPS mode, the dependence of the scattering characteristic on the direction of the azimuthal angle is not specifically detected. The liquid crystal display element of the IPS mode does not include phase plates.

Other

The above description illustrates a prism plate that has triangular grooves. The grooves of the prism plate are not limited by this in shape and can also be rounded and consist of semicircular maximum points and minimum points.

In addition, in the above description, the number of prism wafers used is two. Prism plates are not limited to this number. For example, options without prism plates or with one (1) prism plate are also applicable.

In addition, in the above description, two scattering plates, i.e. an upper diffuser plate 70 and a lower diffuser plate 72 are provided in the backlight unit 60. Only one of the upper diffuser plate 70 and the lower diffuser plate 72 can be provided in the backlight unit 60.

Additionally, in the above description, the upper diffuser plate 70 and the lower diffuser plate 72 are made of the same material. The upper diffuser plate 70 and the lower diffuser plate 72 can also be made of various materials.

Industrial applicability

The backlight module and the liquid crystal display device of the present invention, which allow the implementation of high-contrast display, are preferably suitable for use in applications of the display device, which must realize high-definition display.

List of reference numbers

10 - liquid crystal display device

20 is a liquid crystal display element

22 - liquid crystal layer

34 - first polarizing plate (polarizing plate on the falling side)

H1 - direction of the absorption axis (absorption axis)

36 - second polarizing plate (polarizing plate on the output side)

H2 - direction of the absorption axis (absorption axis)

40 - reflective polarizing film with the effect of increasing brightness

60 - backlight module

64 - light guide plate

66 - the first prism plate (prism plate)

67 - groove

P1 - groove direction (prism axis)

68 - the second prism plate (prism plate)

69 - groove

P2 - groove direction (prism axis)

70 - upper diffusion plate (diffusion plate)

72 - lower diffusion plate (diffusion plate)

80 - light exit plane

R is the orientation region.

Claims (18)

1. A liquid crystal display device comprising:
a liquid crystal display element including a liquid crystal layer, a polarizing plate on the side of light incidence and a polarizing plate on the side of light exit, wherein a polarizing plate on the side of light incidence and a polarizing plate on the light exit side are provided on both sides of the liquid crystal layer, respectively; and
a backlight unit causing light incident through the light exit plane to fall onto the liquid crystal display element,
moreover, the backlight module is provided in such a way that the light incident from the backlight module on the liquid crystal display element in the diagonal direction, which causes the emission of light with a high probability from the liquid crystal display element in its normal direction, has a lower light intensity than the light incident from the backlight module to the liquid crystal display element in another diagonal direction. 2. The liquid crystal display device according to claim 1, wherein the backlight includes a light guide plate, a diffusion plate, and one or more prism plates. 3. The liquid crystal display device according to claim 1 or 2, further comprising a reflective polarizing film with a brightness enhancement effect provided between the liquid crystal display element and the backlight unit. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal display element and the backlight unit are provided close to each other. 5. The liquid crystal display device according to claim 1, wherein the distance between the liquid crystal display element and the backlight module is at least 0 mm and not more than 10 mm. 6. The liquid crystal display device according to claim 2, in which the diagonal direction that causes the emission of light with high probability from the liquid crystal display element in its normal direction and the axis of the prism of the prism plate form an angle of not less than 20 ° and not more than 70 ° or not less than 110 ° and not more than 160 °. 7. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a vertical alignment mode of linear polarization type, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -25 ° and not more than 25 ° or an angle of not less than 65 ° and not more than 115 °. 8. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a vertical alignment mode of linear polarization type, and the absorption axis of the polarizing plate on the incident side of the light and the axis of the prism of the prism plate form an angle of not less than -15 ° and not more than 15 ° or an angle of not less than 75 ° and not more than 105 °. 9. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a vertical alignment mode of linear polarization type, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -5 ° and not more than 5 ° or an angle of not less than 85 ° and not more than 95 °. 10. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a vertical alignment mode of circular polarization type, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -43 ° and not more than 7 ° or an angle of not less than 47 ° and not more than 97 °. 11. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a vertical alignment mode of circular polarization type, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -33 ° and not more than -3 ° or an angle of not less than 57 ° and not more than 87 °. 12. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a vertical alignment mode of circular polarization type, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -23 ° and not more than -13 ° or an angle of not less than 67 ° and not more than 77 °. 13. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a TN mode, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -25 ° and not more than 25 ° or an angle of not less than 65 ° and not more than 115 °. 14. The liquid crystal display device according to claim 2, in which
the liquid crystal display element is a liquid crystal display element with a TN mode, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -15 ° and not more than 15 ° or an angle of not less than 75 ° and not more than 105 °. 15. The liquid crystal display device according to claim 1, in which
the liquid crystal display element is a liquid crystal display element with a TN mode, and
the axis of absorption of the polarizing plate on the side of the incidence of light and the axis of the prism of the prism plate form an angle of not less than -5 ° and not more than 5 ° or an angle of not less than 85 ° and not more than 95 °. 16. The liquid crystal display device according to claim 1, in which there are two prism plates, the axis of the prisms of which intersect each other at right angles. 17. The liquid crystal display device according to claim 1, in which the light exiting through the light exit plane of the backlight module has a half-width of not more than 44 °. 18. The liquid crystal display device according to 17, in which the half-width is at least 20 ° and not more than 40 °.

Images